Photoinduced Electron Donor Acceptor Complex-Enabled α-C(sp)-H Alkenylation of Amines.

Allylic amines are prevalent and vital structural components present in many bioactive compounds and natural products. Additionally, they serve as valuable intermediates and building blocks, with wide-ranging applications in organic synthesis. However, direct α-C(sp)-H alkenylation of feedstock amines, particularly for the preparation of α-alkenylated cyclic amines, has posed a longstanding challenge. Herein, we present a general, mild, operationally simple, and transition-metal-free α-alkenylation of various readily available amines with alkenylborate esters in excellent E/Z - and diastereoselectivities. This method features good compatibility with water and oxygen, broad substrate scope, and excellent functional group tolerance, thereby enabling the late-stage modification of various complex molecules. Mechanistic studies suggest that the formation of a photoactive electron donor-acceptor complex between 2-iodobenzamide and the tetraalkoxyborate anion, which subsequently undergoes photoinduced single electron transfer and intramolecular 1,5-hydrogen atom transfer to generate the crucial α-amino radicals, is the key to success of this chemistry.